Coronary aneurysm associated with DES

Coronary aneurysm associated with DES

Coronary aneurysm can be associated with drug eluting stents as a long term sequelae of positive remodeling of the vessel wall. This could be a response to the effect of the drug being eluted or hypersensitivity to the polymer coating which elutes the drug. Sirolimus eluting stents are composed of iron, nickel, chromium and molybdenum and the coating contains polymethacrylates and polyolefin copolymers. Sirolimus is an immunosuppressant drug which causes suppression of vascular smooth muscle and neointimal proliferation at the site of stent implantation. Sirolimus is completely eluted over a few months while the other components of the stent remain in the vascular wall. Pathological studies in the aneurysmal segments have documented hypersensitivity vasculitis with infiltration of plasma cells, lymphocytes, eosinophils and macrophages, involving all the three layers of the vessel, namely intima, media and adventitia.

Treatment options for coronary aneurysm associated with DES include ligation with bypass grafting, covered stents and just conservative management with antiplatelet therapy for smaller aneurysms with less risk of rupture. Covered stents use polytetrafluoroethylene (PTFE). PTFE can be rolled in a thin multilayer to cover the stent so that it can expand four to five times the crimped stent diameter without breakage while balloon expanding the stent. Negative charge of the polymer prevents coagulation of blood protein and limits platelet activation and thrombus formation. PTFE used for vascular application is known as expanded PTFE (ePTFE). This is ensured by a manufacturing process which modifies the solid material into a porous lattice. This makes it balloon expandable along with the metal component of the stent. To avoid disruption of the PTFE, care has to be used in selecting the balloon length so that the total balloon length including the tapered ends should match the PTFE membrane. Some PTFE stents incorporate a synthetic peptide P-15, a cell adhesion protein to promote endothelialization. There are reports that PTFE covered stents may have a higher incidence of restenosis and thrombosis.